To dye keratin-containing fibers, use is generally made of either direct dyes or oxidation dyes, which arise through oxidative coupling of one or more developer components with one another or with one or more coupler components. The coupler and developer components are also known as oxidation dye precursors.
The developer components used are conventionally primary aromatic amines with a further free or substituted hydroxyl or amino group located in para or ortho position, diaminopyridine derivatives, heterocyclic hydrazones, 4-aminopyrazolone derivatives and 2,4,5,6-tetraminopyrimidine and the derivatives thereof.
Particular representatives are for example p-phenylenediamine, p-tolylenediamine, 2,4,5,6-tetraminopyrimidine, p-aminophenol, N,N-bis-(2′-hydroxyethyl)-p-phenylenediamine, 2-(2,5-diaminophenyl)ethanol, 2-(2,5-diaminophenoxy)ethanol, 1-phenyl-3-carboxyamido-4-aminopyrazol-5-one, 4-amino-3-methylphenol, 2-aminomethyl-4-aminophenol, 2-hydroxymethyl-4-aminophenol, 2-hydroxy-4,5,6-triaminopyrimidine, 2,4-dihydroxy-5,6-diaminopyrimidine, 2,5,6-triamino-4-hydroxypyrimidine and 4,5-diamino-1-(2-hydroxyethyl)pyrazole.
The coupler components used are generally m-phenylenediamine derivatives, naphthols, resorcinol and resorcinol derivatives, pyrazolones, m-aminophenols and substituted pyridine derivatives. Particularly suitable coupler substances are α-naphthol, 1,5-, 2,7- and 1,7-dihydroxynaphthalene, 5-amino-2-methylphenol, m-aminophenol, resorcinol, resorcinol monomethyl ether, m-phenylenediamine, 2,4-diaminophenoxyethanol, 2-amino-4-(2-hydroxyethylamino)-anisole (Lehmann blue), 1-phenyl-3-methylpyrazol-5-one, 2,4-dichloro-3-aminophenol, 1,3-bis-(2,4-diaminophenoxy)propane, 2-chlororesorcinol, 4-chlororesorcinol, 2-chloro-6-methyl-3-aminophenol, 2-methylresorcinol, 5-methylresorcinol, 3-amino-6-methoxy-2-methylaminopyridine and 3,5-diamino-2,6-dimethoxypyridine.
Although intense dyeing results with good fastness properties may be achieved with oxidation dyes, the color generally develops under the influence of oxidizing agents such as for example H2O2, which may in some cases result in damage to the fiber. Moreover, some oxidation dye precursors or certain mixtures of oxidation dye precursors occasionally have a sensitizing effect in people with sensitive skin. Direct dyes are applied under gentler conditions, but their disadvantage is that the fastness properties of the dyeing results are often only inadequate.
Accordingly, it is desirable to provide dyeing agents for keratin-containing fibers, in particular human hair, which are at least equal in quality to conventional oxidation dyeing agents with regard to color depth and fastness properties, such as for example light, rubbing and washing fastness and perspiration and cold wave fastness, but without its being essential to use oxidizing agents such as for example H2O2. In addition, it is desirable to provide dyeing agents that do not have any or have only very slight sensitization potential and have no mutagenic effect.